VI. Polarity

A. Polarity The bonding pairs of electrons in covalent bonds are pulled by the nuclei

A. Polarity Cont. Electronegativity values determine the charge distribution in a covalent bond electronegativity: a measure of an atom’s attraction for electrons

B. Nonpolar Covalent Bond Bond between two nonmetal atoms with the same (or extremely close) electronegativity. Bonded electrons are shared equally Ex: H2, O2, N2

C. Polar Covalent Bond Bond between 2 nonmetal atoms with different electronegativity values. Bonded electrons are shared unequally. Atom with higher electronegativity pulls more strongly and has a partial negative charge Atom with lower electronegativity pulls less strongly and has a partial positive charge

D. Polar Molecules In a polar molecule, one end of the molecule is slightly negative and the other end is slightly positive. A molecule that has two poles (opposite charges) is called a dipolar molecule, or dipole.

E. Determining Polar/Nonpolar/Ionic Use difference in electronegativity values to determine the type of bond. Difference Type of Bond 0.0 – 0.4 Nonpolar covalent 0.4 – 1.0 Moderately polar covalent 1.0 – 2.0 Very polar covalent ≥ 2.0 Ionic

Example #1 Determine the type of bond between H and Cl. H = 2.1 Cl = 3.0

H and Br C and O Br and Br K and Cl P and F Example 2 H = 2.1 Br = 3.0 C = 2.5 O = 3.5 K = 0.8 Cl = 3.0 P = 2.1 F = 4.0 H and Br C and O Br and Br K and Cl P and F